Originally Posted by Mothra
The thing with bending the calipers is you should do it just once. Eventually the pads will wear flat and squealing will happen again. Do you then bend the calipers even more? Every single time the pads wear flat? No, after that first time, the pads will wear at an angle relative to the backing-plate. When the surface gets parallel to the rim, you just flip the pads 180-degrees and you'll have toe-in again.
Actually, the reason for toe-in is to cause pads to wear evenly from the beginning. If you don't toe them in, the forward motion of the rim as the pads touch them causes their heels to dig in while the toes lift up, causing them to wear unevenly and not be maximally effective. So it's just the other way around - if you
don't toe them in, your brake pads will eventually wear flat. The idea of toeing in is to avoid this period of less-than-maximum braking and squealing, which can be worse if the entire surface of the pad isn't contacting the rim.